The invention relates to an apparatus for rotating an information disc. The apparatus comprises a deck plate and a turntable journalled in the deck plate for rotation about an axis. The turntable comprises a supporting surface for the information disc, a centring member for centring the information disc on the turntable relative to the axis of rotation, and a clamping device for clamping the information disc onto the turntable, which device comprises a disc-pressure means and a support for the disc-pressure means, which support is movable between an operating position and a rest position. The disc-pressure means is pressed against the information disc on the turntable in the operating position of the support, and is rotatable relative to the support, which support as it moves from the operating position to the rest position, cooperates with the disc-pressure means to move said means away from the information disc and thereby release the information disc. While in its rest position, the support carries the disc-pressure means, and an electric drive unit comprising a stator section and a rotor section for rotating the disc, which is supported by the turntable, in the operating position of the support.
Netherlands patent application No. 8202163 (PHN 10.359, herewith incorporated by reference) describes an optical-disc apparatus in which the turntable is mounted on a spindle of a drive motor, which spindle is rotatable about the axis of rotation. The drive motor, which is supported in the deck plate, is situated underneath the turntable. On the same side of the turntable there is arranged a focusing device comprising an objective by means of which a radiation beam produced by a laser source can be focused on the lower surface of an optical disc placed on the turntable and by means of which the beam reflected by the disc is diverted towards photoelectric information-detection means of the apparatus. In order to enable the entire information surface of the disc to be scanned, which surface extends between a circle of small radius and a circle of larger radius, the objective is mounted so as to be radially movable inside the apparatus. However, this means that in a radial direction the space available for the drive motor is limited and is dictated by the required radial freedom of the objective. Therefore, the drive motor of the known apparatus is required to have a comparatively great axial length in order to be able to produce the motor power and motor torque necessary for driving the turntable, so that the height of the apparatus is comparatively large.
Currently, there is a trend to minimize the height of such apparatus due to current design concepts for audio and video equipment and the need for small portable equipment and equipment suitable for mounting in cars. However, if the height is reduced this also means that the axial length of the drive motor must be reduced. Since the diameter of the drive motor cannot be increased, problems may arise in respect of maintaining the required motor specifications, in particular the power and torque. This may necessitate additional steps such as the use of high grade magnetic materials in the motor, which renders the motor more expensive, or reducing the axial length of the motor only to a limited extent.